Following its arrival onboard shuttle Atlantis during STS-129, the CRS UHF Communication Unit (CUCU) – a key element for the upcoming demonstration of SpaceX’s Dragon capsule – has passed a series of tests on the International Space Station (ISS), allowing the commercial company to confirm its successful activation.
Atlantis and ISS aid Dragon’s future:
The Commercial Orbital Transportation Services (COTS) Ultra High Frequency (UHF) Communication Unit rode in the middeck stowage locker on Atlantis during STS-129 late in 2009, before being handed over to ISS crewmembers ahead of the demonstration flights.
The new system will allow ISS crewmembers to monitor and command approaching or departing Dragon spacecraft during cargo delivery missions to the orbiting laboratory.
Led by SpaceX’s soon-to-launch Falcon 9 launch vehicle, the Dragon spacecraft has three demonstration flights planned for its cargo supply version. Dragon is also in the mix to become the a crew transport vehicle for US astronauts heading to the ISS after the shuttle retires.
Among the demo tests will be the capsule’s establishment of communication and relative GPS with ISS at 23 km, before carrying out a fly-by at 10km below the Station, leading to a final demo, which will involve Dragon’s debut rendezvous and capture at the ISS, with the Space Station Remote Manipulator System (SSRMS) transitioning the capsule for mating to the Node 2 Nadir port.
Demo cargo is yet to be manifested for transfer to/from ISS during its 14 day stay on Station, and the schedule remains open-ended, based on the success of Falcon 9’s debut – currently scheduled for next month.
“CUCU provides a bi-directional, half-duplex communications link between Dragon and ISS using existing ISS UHF Space to Space Station Radio (SSSR) antennas, which provides a communication path between MCCX (SpaceX) and Dragon during proximity operations and a command security between ISS and Dragon,” noted STS-129 Flight Readiness Review (FRR) documentation on L2.
“Unit mounted inside a rack on ISS and connected to ISS data, audio, and UHF antenna resources – provides a separate Crew Command Panel (CCP) for crew interface to Dragon.”
The on-orbit checkout of the CUCU began January 25, 2010, when astronaut Jeff Williams, ISS Expedition 22 Commander, who has since returned to Earth, worked with ground-based team members at SpaceX headquarters and ISS mission control in Houston to power-up and check out the new system.
On March 11, SpaceX and NASA Houston performed an additional series of tests, using the new system to send communications between the ISS and the NASA Dryden ground station. This provided a baseline of the radio frequency performance and confirmed the first set of antennas performed as expected and is ready for mission operations.
Additional testing is expected for a second set of antennas as well as ongoing verification of the overall system.
The tests employed live video and telemetry links from the ISS to verify the hardware’s functionality, broadcast and reception signal strengths, and the system’s stability over long-duration operations.
“The success of this series of tests speaks to our close collaboration with NASA as well as the SpaceX process that allowed the rapid development of this new hardware,” said Marco Villa, SpaceX Mission Operations Manager.
“Furthermore, the January tests marked the first official joint operations between SpaceX Mission Control in California, and NASA Mission Control in Houston. Everything went smoothly, and we eagerly anticipate the upcoming Dragon visits to the ISS.”
Developed by SpaceX under a NASA Space Act Agreement, the new system allows for communication between the ISS and SpaceX’s Dragon spacecraft while in the vicinity of the ISS. Its design leverages the abilities of the ISS communication systems, providing data exchange with ground-based mission control.
Designed from the beginning to transport crew, SpaceX’s Falcon 9 and Dragon spacecraft were selected by NASA to transport cargo to and from the ISS starting in 2011. The $1.6B contract represents 12 flights for a minimum of 20 tons to and from the ISS. The first demonstration flights under the COTS program are scheduled for 2010, following the inaugural launch of SpaceX’s Falcon 9 rocket.
This was the second time an orbiter had provided assistance to SpaceX, following Endeavour’s role with the DragonEye (DE) Detailed Test Objective (DTO) box – with flash LIDAR and data acquisition unit – during STS-127.